Method of forming a black tantalum alloy, a tantalum alloy, and articles formed therefrom

ABSTRACT

The invention provides tantalum alloys, methods for forming tantalum alloys having a luminous, black, ceramic surface, and articles, such as, but not limited to, jewelry and watches, formed from the tantalum alloys.

FIELD OF THE INVENTION

The present invention relates generally to metal alloys and methods for forming such alloys, particularly to forming tantalum alloys, and most particularly to forming a tantalum alloy having a luminous, black, ceramic surface and making articles, such as, but not limited to, jewelry and watches, therefrom.

BACKGROUND OF THE INVENTION

The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 CFR §1.56(a) exists.

At least with respect to jewelry, “Black is beautiful” may be an understatement as jewelry pieces with black finishes are extremely popular. U.S. Pat. No. 8,262,814 to Zak discloses a method, and articles therefrom, for providing a hard, abrasion-resistant, attractive, oxide surface layer of selectable thickness and having an outer appearance within the scale from gray to blackness, to a zirconium titanium alloy article by heating the article in an oxygen containing atmosphere. U.S. Pat. No. 6,759,134 to Rosenberg discloses a process of forming a metallic article having a black oxide/ceramic surface and articles produced by the method using a titanium based alloy. Chinese Patent No. CN101215662 to RONG LIU discloses a tungsten alloy used for jewelry and ornamental article, and preparation method thereof.

Although none of the above-identified patents discusses the use of tantalum as the primary alloy component, tantalum has been used in jewelry. One method to give tantalum, or most other metals, a desired appearance is through the use of plating or coating.

Heretofore, if an object was coated or plated by means of plasma vapor deposition (PVD), the underlying surface remained the same as before the plating. If the object was scratched, the contrasting metal showed through. In order to effect a repair, the object would have to be sent to a specialty company for replacement of the PVD coating as PVD coating is done in a laboratory with strict scientific procedure and with highly sophisticated equipment. As a result, the cost to repair is quite high.

SUMMARY OF THE INVENTION

One aspect of the invention concerns the blackening of tantalum by means of a heat process for use in jewelry and/or watches. By utilizing high heat, tantalum can be made permanently black. During the heating process, generally at 700-900 C°, using induction heat or in a conventional oven, a black oxide layer forms. Additionally, in a plasma vapor deposition chamber, under vacuum, an induction arc is provided and targets if Ti/Zr alloy are vapor deposited on tantalum, also creates a black oxide surface or coating. The black ceramic, luminous surface is substantially an oxide of zirconium.

Blackening of tantalum provides a new, heavy material hereto provided only by tungsten, a material that is not biologically friendly. Tantalum is virtually biologically inert. Thus, any products made from this material, i.e. blackened tantalum, can be considered hypo-allergenic. This material can be used in jewelry applications and/or watches; for example, but not limited to, in rings, bracelets, necklaces, earrings, and both decorative and functional parts for watches.

With some embodiments of the black tantalum alloy herein disclosed, the surface and to a depth underlying the surface of several microns become black in color. In the event an object is scratched, the surface can be re-polished and the blackening can be re-effected by a local qualified repair person with tools and equipment generally found on a typical jewelry repair bench. The cost for repair are quite minimal. Thus, inexpensive and durable jewelry and/or watches can be made using the disclosed black tantalum alloy.

In one aspect, the invention provides a composition including a homogeneous mixture. The composition has or comprises between about 45% and about 75% by weight of tantalum; between about 20% and about 45% by weight of zirconium; between about 0% and about 35% by weight of niobium; and a balance by weight of a metal selected from the group consisting of titanium, molybdenum, hafnium, vanadium, silicone, chromium, and combinations thereof.

A “homogeneous” mixture refers to a mixture of a uniform nature or a mixture having constant properties.

In one embodiment, the homogeneous mixture is a mixture of metal bars that has been melted in a vacuum to form a solid, homogeneous mixture of metals. The metal bars utilized range in size from about 10 cm to about 25 cm. The composition and/or homogeneous mixture has a luminous, black ceramic surface or coating.

In another embodiment, the homogeneous mixture is a mixure of metal powders that has been mixed in ambient air and melted in a vacuum to form a solid, metal form. The particles of the metal powders range in size from about 0.3 μm to about 10 μm. The composition and/or solid, metal form has a gray color, but will attain a black ceramic surface upon heating in an oxygen-rich atmosphere.

The described powder compositions may be formed into almost any shape, including, but not limited to bars, rods, wire, tubing, pipes, sheets, and rings. The composition can also be shaped in a mold having any desired geometry or shape.

In another aspect, the invention provides jewelry work pieces, having a luminous, black ceramic surface, formed or made from the described compositions.

A “jewelry work piece” refers both to a complete, finished piece of jewelry or watch and to any individual part which can be used to form jewelry and/or watches. The work pieces may be decorative and/or functional in nature.

In another aspect, the invention provides a method for making a composition including a mixture having or comprising between about 45% and about 75% by weight of tantalum; between about 20% and about 45% by weight of zirconium; between about 0% and about 35% by weight of niobium; and a balance by weight of a metal selected from the group consisting of titanium, molybdenum, hafnium, vanadium, silicone, chromium, and combinations thereof.

One embodiment of the method includes providing a portion of tantalum bars by measuring between about 45% and about 75% by weight of tantalum of the total weight of the composition; providing a portion of zirconium bars by measuring between about 20% and about 45% by weight of zirconium of the total weight of the composition; providing a portion of niobium bars by measuring between about 0% and about 35% by weight of niobium of the total weight of the composition; providing a balance portion of a metal bar selected from the group consisting of titanium, molybdenum, hafnium, vanadium, silicone, chromium, and combinations thereof by measuring the balance portion of the selected metal bar to the total weight of the composition; preparing a mixture of metal bars by mixing the portions of tantalum bars, zirconium bars, niobium bars, and the balance portion of the selected metal bar to prepare the mixture of metal bars; and melting the mixture of metal bars to form the composition.

This method can also include heating the composition in an atmosphere containing 15-100% concentration of oxygen at a temperature in a range of about 400-900 C.° for a time period of about 5-60 minutes to form a luminous, black ceramic surface on the composition.

One embodiment of this method includes providing a portion of tantalum powder by measuring between about 45% and about 75% by weight of tantalum of the total weight of the composition; providing a portion of zirconium powder by measuring between about 20% and about 45% by weight of zirconium of the total weight of the composition; providing a portion of niobium powder by measuring between about 0% and about 35% by weight of niobium of the total weight of the composition; providing a balance portion of a metal powder selected from the group consisting of titanium, molybdenum, hafnium, vanadium, silicone, chromium, and combinations thereof by measuring the balance portion of the selected metal powder to the total weight of the composition; preparing a mixture of metal powder by mixing the portions of tantalum powder, zirconium powder, niobium powder, and the balance portion of the selected metal powder to prepare the mixture of metal powders; and melting the mixture of metal powders in temperature cycles varying between about 1000-3000 C.° in a vacuum for a time period of about 2-5 days to form the composition.

The method can also include heating the composition in an atmosphere containing 15-100% concentration of oxygen at a temperature in a range of about 400-900 C.° for a time period of about 5-60 minutes to form a luminous, black ceramic surface on the composition. Any of the methods described herein can further include shaping or forming the composition into almost any shape, including, but not limited to, bars, rods, wire, tubing, pipes, sheets, and rings.

In a another aspect, the invention provides a black tantalum alloy and jewelry work pieces made using any of the described methods.

In yet another aspect, the invention provides a piece of jewelry including any of the described compositions and/or alloys bound to gemstones or other metals.

Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings, wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawing constitutes a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and the attendant advantages and features thereof, may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent detailed description. The embodiments illustrated in the drawings are intended only to exemplify the invention and should not be construed as limiting the invention to the illustrated embodiments.

FIG. 1 shows a cross-section of a jewelry work piece made with the blackened tantalum alloy of the invention.

FIGS. 2A-C show a carbide press (A), a die having a diamond shape (B), and a die having a trapezoid shape (C).

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates particularly to forming a tantalum alloy having a luminous, black, ceramic surface and making articles, such as jewelry and watches, therefrom.

The tantalum alloy described herein is a natural oxide of tantalum, niobium, and zirconium. The primary luminous surface is caused by the oxide of zirconium.

Production of the Alloy

Process One: Metal bars of various metal containing between about 45% and about 75% weight of tantalum, between about 20% and about 45% zirconium by weight, between about 0% and about 35% niobium, and a balance by weight of a metal selected from titanium, molybdenum, hafnium, vanadium, silicone, chromium, and combinations thereof are melted in a vacuum to a heat necessary to cause homogeneous mixtures of all metals. In an exemplary embodiment, there is between about 10% and about 35% by weight of niobium. Upon cooling within the vacuum, the subsequent bar is rolled into plate or centrifugally swaged into round bars. Further drawing through progressively smaller dies can produce wire or tubing.

Vacuum Process: Vacuum pressure ranges from about 1 Mpa to about 5 Mpa. The temperature is first increased at a rate not greater than about 15° F./minute (about 8° C./minute) to a temperature in the range of about 1400-1900° F. (about 760-1050° C.). The temperature is held for about 6-36 hours at this temperature, then raised to about 2000-2900° F. (about 1100-1600° C.) and held at this temperature for about 1 to about 3 days. Temperature is then gradually reduced by about 15° F. (about 8° C.) until the temperature reaches about 200° F. (about 100° C.). Pressure is then relieved to standard.

Process Two: Fine powders, from about 0.3 μm to about 10 μm in size, of various metals containing between about 45% and about 75% by weight of tantalum, between about 20% and about 45% zirconium by weight, between about 0% and about 35% niobium, and a balance by weight of a metal selected from titanium, molybdenum, hafnium, vanadium, silicone, chromium, and combinations thereof are mixed in ambient air to produce a homogeneous mixture of all metal powders. In an exemplary embodiment, there is between about 10% and about 35% by weight of niobium. The mixture is placed into molds of varying sizes and shapes and, with the use of high tonnage equipment, is pressed into the molds. The resultant parts or molds are placed into a sintering oven for 2-5 days at varying time and temperature cycles between 1000-3000 C.° which, in vacuum, caused the powdered mixture to be transformed into a solid, metal form.

Pressing Process: A carbide press 1, as shown in FIG. 2A (perspective view), can be used to mold the powder mixture. At the top of the press is a first ram 2. The powder 4 is poured into the press cavity 3, i.e. the die, and then the first ram 2 comes down and compresses the powder 4. There is 500 ton hydraulic pressure on the first ram 2. Once the powder 4 is fully pressed, the first ram 2 is withdrawn. A second ram 5 is present at the bottom of the press cavity 3. The second ram 5 comes up and pushes the pressed powder out of the press cavity 3. A die shaped like a diamond 6, to press a diamond shape, is shown in FIG. 2B (top view) and a die shaped like a trapezoid 7, to press a trapezoid shape, is shown in FIG. 2C (top view). One die can be used to produce many different widths of the same shape.

Blackening After Production of the Alloy

A tantalum alloy made by either of the above processes is heated by electrical induction or heated in an atmospheric oven, in the presence of an atmosphere containing about 15-100% concentration of oxygen at a temperature of between about 400 C.° and about 900 C.° for a period of between about 5 to about 60 minutes.

This blackening process produces a tantalum alloy having a luminous, black ceramic surface. Zirconium contributes the luminous, ceramic surface.

The blackened tantalum alloy can be made into any jewelry work piece. FIG. 1 shows a cross-section of a jewelry work piece made with the blackened tantalum alloy 10 having darkened surface 20.

All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. All references cited herein are expressly incorporated by reference in their entirety. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. It is to be understood that while a certain form of the invention is illustrated, it is not intended to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification. One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The compositions, alloys, jewelry, watches, jewelry work pieces, methods, procedures, and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention. Although the invention has been described in connection with specific, preferred embodiments, it should be understood that the invention as ultimately claimed should not be unduly limited to such specific embodiments. Indeed various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the invention.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention.

In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. There are many different features to the present invention and it is contemplated that these features may be used together or separately. Thus, the invention should not be limited to any particular combination of features or to a particular application of the invention. Further, it should be understood that variations and modifications within the spirit and scope of the invention might occur to those skilled in the art to which the invention pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention. 

What is claimed is:
 1. A composition including a homogeneous mixture, the composition comprising: between about 45% and about 75% by weight of tantalum; between about 20% and about 45% by weight of zirconium; between about 0% and about 35% by weight of niobium; and a balance by weight of a metal selected from the group consisting of titanium, molybdenum, hafnium, vanadium, silicone, chromium, and combinations thereof.
 2. The composition according to claim 1, wherein the homogeneous mixture is a mixture of metal bars that has been melted in a vacuum to form a solid homogeneous mixture of metals.
 3. The composition according to claim 2, wherein there is between about 10% and about 35% by weight of niobium.
 4. The composition according to claim 2, wherein the composition has a luminous, black, ceramic surface.
 5. The composition according to claim 2, wherein the composition is formed into a shape selected from the group consisting of bars, rods, wire, tubing, pipes, sheets, and rings.
 6. A jewelry work piece formed from the composition of claim
 4. 7. The composition according to claim 1, wherein the homogeneous mixture is a mixture of metal powders that has been mixed in ambient air and melted in a vacuum to form a solid metal form.
 8. The composition according to claim 7, wherein particles of the metal powders range in size from about 0.3 μm to about 10 μm.
 9. The composition according to claim 7, wherein the solid metal form has a luminous, black, ceramic surface.
 10. The composition according to claim 7, wherein there is between about 10% and about 35% by weight of niobium.
 11. A jewelry work piece formed from the composition of claim
 9. 12. A method for forming the composition of claim 1, the method comprising: providing a portion of tantalum bars by measuring between about 45% and about 75% by weight of tantalum of the total weight of the composition; providing a portion of zirconium bars by measuring between about 20% and about 45% by weight of zirconium of the total weight of the composition; providing a portion of niobium bars by measuring between about 0% and about 35% by weight of niobium of the total weight of the composition; providing a balance portion of a metal bar selected from the group consisting of titanium, molybdenum, hafnium, vanadium, silicone, chromium, and combinations thereof by measuring the balance portion of the selected metal bar to the total weight of the composition; preparing a mixture of metal bars by mixing the portions of tantalum bars, zirconium bars, niobium bars, and the balance portion of the selected metal bar to prepare the mixture of metal bars; and melting the mixture of metal bars to form the composition.
 13. The method according to claim 12, further comprising heating the composition in an atmosphere containing 15-100% concentration of oxygen at a temperature in a range of about 400-900 C.° for a time period of about 5-60 minutes to form a luminous, black ceramic surface on the composition.
 14. The method according to claim 12, further comprising shaping the composition into a shape selected from the group consisting of bars, rods, wire, tubing, pipes, sheets, and rings.
 15. A black tantalum alloy formed by the method of claim
 13. 16. The method according to claim 13, wherein there is between about 10% and about 35% by weight of niobium.
 17. A method for forming the composition of claim 7, the method comprising: providing a portion of tantalum powder by measuring between about 45% and about 75% by weight of tantalum of the total weight of the composition; providing a portion of zirconium powder by measuring between about 20% and about 45% by weight of zirconium of the total weight of the composition; providing a portion of niobium powder by measuring between about 0% and about 35% by weight of niobium of the total weight of the composition; providing a balance portion of a metal powder selected from the group consisting of titanium, molybdenum, hafnium, vanadium, silicone, chromium, and combinations thereof by measuring the balance portion of the selected metal powder to the total weight of the composition; preparing a mixture of metal powder by mixing the portions of tantalum powder, zirconium powder, niobium powder, and the balance portion of the selected metal powder to prepare the mixture of metal powders; and melting the mixture of metal powders in temperature cycles varying between about 1000-3000 C.° for a time period of about 2-5 days to form the composition.
 18. The method according to claim 17, further comprising heating the composition in an atmosphere containing 15-100% concentration of oxygen at a temperature in a range of about 400-900 C.° for a time period of about 5-60 minutes to form a luminous, black ceramic surface on the composition.
 19. The method according to claim 17, further comprising shaping the composition into a shape selected from the group consisting of bars, rods, wire, tubing, pipes, sheets, and rings.
 20. A black tantalum alloy formed by the method of claim
 18. 21. The method according to claim 18, wherein there is between about 10% and about 35% by weight of niobium. 